技術標籤：Mysqlmysql資料庫

1.表結構

CREATE TABLE `user_info` (
  `u_id` int(2) unsigned NOT NULL AUTO_INCREMENT COMMENT '編號',
  `u_name` varchar(255) DEFAULT NULL COMMENT '姓名',
  `u_gender` int(1) DEFAULT NULL COMMENT '0.女 1.男',
  `u_age` int(2) DEFAULT NULL COMMENT '年齡',
  `u_number` varchar(255) DEFAULT NULL COMMENT '學號',
  PRIMARY KEY (`u_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 

2.表資料

SELECT * from user_info;

3.查詢重複（學號）資料

select *,count(u_number) duplicate_count from user_info group by u_number having count(u_id)>1;

4.刪除重複資料

delete from user_info where u_id not in (select a.u_id from ((select min(u_id) u_id from user_info group by u_number) a));

5.刪除後查詢結果